Recurrent urinary tract infection: Laboratory Identification

Enterococcus ID

  • Illustrated in this composite photograph is the gram stain of Enterococcus species (upper), illustrating gram positive cocci arranged in pairs and short chains.
  • The viridans streptococci generally form gram positive cocci in long chains; the gram-positive cells of S. pneumoniae, on the other hand, may appear similar in gram stain.
  • In the lower right is shown a 6.5% NaCl tube. The turbidity indicates growth, a unique characteristic for Enterococcus species.
  • In the lower left frame is a picture of a bile esculin hydrolysis slant, showing a positive reaction (black pigment) characteristic of Enterococcus species. The streptococci are uniformly negative.
  • Some strains of Leuconostoc species and Pediococcus species can grow in 6.5% NaCl and are bile-esculin positive; however, they should be ruled out because of the negative PYR reaction.

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